Roll film, method for producing roll film, method for producing copper-clad laminate and method for producing printed board

ABSTRACT

To provide a dielectric film which is excellent in dielectric properties and stability in the electric corrosion test and which is suitable for producing a high-precision printed board. 
     A roll film comprising a melt-processable fluororesin as the main component and having a thickness of from 1 to 100 μm, the dimensional change rate of which is less than 1.0%, in terms of an absolute value, in each of MD and TD, when heated at 150° C. for 30 minutes and then cooled to 25° C., based on the dimension at 25° C.

TECHNICAL FIELD

The present invention relates to a roll film and methods for producing aroll film, a copper-clad laminate and a printed board.

BACKGROUND ART

Applications of printed boards extend over various electric appliancesand systems such as cell phones, personal computers, automobiles, onlinesystems and satellites. In recent years, high frequency signals tend tobe used, and patterned circuits of printed boards tend to be finer,since the volume of information is increasing.

In production of printed boards, a copper-clad laminate having a copperfoil laminated on a surface of a dielectric film is used in general. Inproduction of a single-side board having the simplest structure, acircuit pattern to be obtained is formed on a copper foil of acopper-clad laminate by screen printing or baking and development of aphotosensitive adhesive film and used, as an etching resist for etchingthe copper foil.

In production of a double-side board and a multi-layer board,through-hole plating is employed for interlayer connection in manycases. In general, in the through-hole plating, inside of a hole for theinterlayer connection and a board surface are covered with a copperplating film by full plating so-called panel plating. A circuit patternis formed by collectively etching a copper foil and a copper platingfilm formed thereon. In recent fine circuit boards, a thin copper foilhaving a thickness of at most 12 μm is used in many cases for improvingthe etching accuracy. Particularly, for forming fine patterns such as aline and space pattern having a line width of 50 μm and a space width ofabout 50 μm, the copper thickness at the time of forming the circuit isreduced, and the etching accuracy can be easily improved by using anultrathin plating copper foil having a thickness of 5 μm.

The evaluation of finish state and the reliability test are conducted onthrough-hole plated printed boards. The evaluation of finish stateincludes three tests of plating thickness, plating shape and platingphysical property. The reliability test focuses on a fatigue lifespanevaluation by temperature cycle and an insulating lifespan evaluationunder constant temperature-constant humidity bias so-called electrolyticcorrosion test. In the electrolytic corrosion test, an inter-patterninsulating reliability test using comb form patterns has been known asan important reliability test (Non-Patent Document 1).

As the dielectric film, a polyimide film (Patent Document 1) and a film(Patent Document 2) made of at least one member selected from the groupconsisting of a polyphenylene ether resin, a polyether sulfone resin, apolyether ether ketone resin and a fluororesin have been known.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: Japanese Patent No. 4,880,911-   Patent Document 2: JP-A-2015-146469

Non-Patent Documents

-   Non-Patent Document 1: Hajime NAKAYAMA, Journal of the Surface    Finishing Society of Japan Vol. 53, (Issue 2), p. 110-115 (2002)

DISCLOSURE OF INVENTION Technical Problem

The electrolytic corrosion test is a constant temperature-constanthumidity bias test between through-holes or between a through-hole andan inner pattern and employed as a comprehensive evaluation test for thestability of through-hole plated parts of e.g. a plating film, a boardand production state. A dielectric film which is excellent in dielectriccharacteristics and stability in the electrolytic corrosion test isdesired for producing a high-precision printed board. However, the filmof Patent Document 1 has a high relative dielectric constant, whereby ahigh transmission property cannot be realized. The film of PatentDocument 2 is poor in the stability in the electrolytic corrosion test.

It is known that fluororesin films are excellent in the dielectriccharacteristics. However, the present inventors have found that printedboards produced by using a roll film of such a fluororesin film arestill insufficient in the stability in the electrolytic corrosion test,and its cause is the dimension stability of the roll film. Thus, it isdifficult to efficiently produce a printed board having excellentstability in the electrolytic corrosion test by using a roll film of afluororesin.

The present inventors have conducted extensive studies and as a result,obtained a roll film of a fluororesin which is excellent in thedimensional stability of a predetermined thickness, which is suitable toproduce a high-precision printed board.

It is an object of the present invention to provide a roll film of afluororesin which is suitable to efficiently produce a printed boardexcellent in the stability in the electrolytic corrosion test, itsproduction method and methods for producing a copper-clad laminate and aprinted board which use the roll film.

Solution to Problem

The present invention provides a roll film, a method for producing aroll film, a method for producing a copper-clad laminate and a methodfor producing a printed board, which have the following embodiments [1]to [15].

[1] A roll film comprising a melt-processable fluororesin as the maincomponent and having a thickness of from 1 to 100 μm, the dimensionalchange rate of which is less than 1.0%, in terms of an absolute value,in each of MD and TD, when heated at 150° C. for 30 minutes and thencooled to 25° C., based on the dimension at 25° C.[2] The roll film according to [1], wherein the ratio of the tensionwhen wound to the dimensional change rate, in terms of an absolutevalue, in MD is from 100 to 1,000,000.[3] The roll film according to [1] or [2], which is used for acopper-clad laminate.[4] The roll film according to any one of [1] to [3], wherein themelt-processable fluororesin is a fluororesin having units derived fromtetrafluoroethylene and units derived from a perfluoro(alkyl vinylether).[5] The roll film according to any one of [1] to [4], wherein themelt-processable fluororesin is a fluororesin having a functional grouphaving an ion scavenging function.[6] The roll film according to any one of [1] to [5], which comprises amelt-processable fluororesin having a functional group having an ionscavenging function and a melt-processable fluororesin other than theabove melt-processable fluororesin as the main component.[7] The roll film according to any one of [1] to [6], which has a layerof the melt-processable fluororesin and a layer of a melt-processablefluororesin having a functional group having an ion scavenging function.[8] The roll film according to any one of [5] to [7], wherein thefunctional group having an ion scavenging function is at least onemember selected from the group consisting of a carbonyl group, a carboxygroup, a carboxylic acid anhydride group (—C(═O)—O—C(═O)—), acarboxylate group, a sulfonyl group, a sulfo group and a sulfonic acidanhydride group (—S(═O)₂—O—S(═O)₂—).[9] The roll film according to any one of [1] to [8], which has athickness of from 3 to 75 μm.[10] A method for producing the roll film as defined in any one of [1]to [9], which comprises subjecting a film comprising themelt-processable fluororesin as the main component and having athickness of from 1 to 100 μm to annealing treatment at from atemperature lower by 210° C. than the melting temperature (Tm) of themelt-processable fluororesin to a temperature lower by 20° C. than Tmand then winding the film.[11] The method according to [10], wherein the annealing treatment iscarried out with a tension of at most 10 N/m applied to the film.[12] The method according to [10] or [11], wherein the film is woundwith a tension of at most 500 N/m applied to the film.[13] A method for producing a copper-clad laminate, which comprisesunwinding the roll film as defined in any one of [1] to [9] and forminga copper layer on a surface of the unwound film.[14] The method according to [13], which forms a copper layer having anAC resistance value of higher than 1.0×10⁻⁹ Ω·cm.[15] A method for producing a printed board, which comprises producing acopper-clad laminate by the method as defined in [13] or [14] andetching the copper layer to form a patterned circuit.

Advantageous Effects of Invention

According to the roll film of the present invention, it is possible toobtain a printed board which is excellent in the stability in theelectrolytic corrosion test.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view schematically illustrating an example of an untreatedfilm production apparatus 100.

FIG. 2 is a view illustrating an example of a schematic structure of abonding apparatus for bonding an untreated film and a substrate.

FIG. 3 is a view illustrating an example of a schematic structure of anannealing treatment apparatus.

FIG. 4 is a cross-sectional view schematically illustrating an exampleof a copper-clad laminate.

FIG. 5 is a cross-sectional view schematically illustrating anotherexample of a copper-clad laminate.

FIG. 6 is a view explaining a pattern used in the electrolytic corrosiontest.

FIG. 7 is a view explaining the method of the electrolytic corrosiontest.

DESCRIPTION OF EMBODIMENTS

In this specification, the meanings of the following terms are asfollows.

“MD” means a machine direction, and “TD” means a transverse direction atright angles to MD.

“Dimensional change rate” is a dimensional change rate when heated to150° C. for 30 minutes and then cooled to 25° C. based on the dimensionat 25° C. and is obtained by the method described in the after describedExamples.

“Melt-processable resin” means a melt flowable resin and means a resinhaving a temperature at which the melt flow rate is from 0.1 to 1,000g/10 min at a temperature higher by 20° C. than the melting point of theresin under a condition of a load of 49N.

“Melt flow rate” means a melt mass flow rate (MFR) of a resin stipulatedin JIS K7210: 1999 (ISO1133: 1997).

“Melting temperature” means a temperature corresponding to the maximumvalue of the melting peak of a resin measured by differential scanningcalorimetry (DSC) method.

“Glass transition temperature” (hereinafter referred to also as Tg) isone of transition temperatures which results from the molecular state inan amorphous region of a resin, and at a temperature lower than Tg, themain chain of the resin is frozen, and the resin becomes glass state. Tgmeans a temperature corresponding to a temperature showing the maximumvalue of tan δ peak measured by the dynamic viscoelasticity measurement(DMA) of a film.

“Unit” in a resin (polymer) means an atomic group formed bypolymerization of a monomer and derived from the monomer. The unit maybe a unit directly formed by a polymerization reaction or may be a unitwherein a part of the unit is converted to another structure bytreatment of the polymer. Hereinafter, the unit derived from a monomermay be simply referred to as “unit of a monomer”.

The expression “to” showing a numerical range is used to include thenumerical values before and after it as the lower limit value and theupper limit value.

Dimensional ratios in FIG. 1 to FIG. 7 are different from actual ratiosfor explanatory convenience.

The roll film of the present invention comprises a melt-processablefluororesin (hereinafter referred to also as “fluororesin”) as the maincomponent, has a thickness of from 1 to 100 μm and has the dimensionalchange rate that is less than 1.0%, in terms of an absolute value, ineach of MD and TD, when heated at 150° C. for 30 minutes and then cooledto 25° C., based on the dimension at 25° C. The roll film of the presentinvention is a wound roll film and preferably a long (belt-like) filmwound into a roll form.

The fluororesin in the present invention is a melt-processable resinhaving units of a fluoroolefin. The fluoroolefin is preferablytetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), vinylidenefluoride (VDF) or vinyl fluoride (VF), particularly preferably TFE.

The melting temperature of the fluororesin is preferably from 260 to320° C., particularly preferably from 280 to 310° C.

MFR of the fluororesin is preferably from 0.1 to 100 g/10 min, morepreferably from 1 to 40 g/10 min, particularly preferably from 5 to 30g/10 min, under a condition of a load of 49N at a temperature higher by20° C. than the melting temperature of the fluororesin. In such a case,the balance between the processing property of the fluororesin and themechanical strength of the roll film tends to be good.

The relative dielectric constant of the fluororesin is preferably atmost 3.0, more preferably at most 2.5, particularly preferably at most2.2. The lower limit of the relative dielectric constant is, forexample, 1.8. In such a case, the roll film is excellent in electriccharacteristics, and a printed board excellent in the transmittingefficiency is obtained.

The relative dielectric constant of the fluororesin may, for example, becontrolled by the type or the content of units of the fluoroolefincontained in the fluororesin.

The storage elastic modulus of the fluororesin is, for example under theannealing treatment conditions in the after-mentioned method forproducing the roll film, preferably at least 1 MPa, more preferably atleast 10 MPa, particularly preferably at least 20 MPa. From theviewpoint of the flexibility of the fluororesin required for continuoustreatment, the upper limit value is 100 MPa. Here, the storage elasticmodulus can be measured by solid dynamic viscoelasticity measurement orthe like.

As the fluororesin, a fluororesin (PFA) having units of TFE and units ofa perfluoro(alkyl vinyl ether) (PAVE), a fluororesin (FEP) having unitsof TFE and units of hexafluoropropylene (HFP), a fluororesin (ETFE)having units of TFE and units of ethylene, a fluororesin (PVDF) havingunits of VDF, a fluororesin (PCTFE) having units of CTFE and afluororesin (ECTFE) having units of ethylene and units ofchlorotrifluoroethylene may be mentioned. PFA is preferred, since aprinted board more excellent in the dimensional stability and the flexresistance and the stability in the electrolytic corrosion test can beobtained. PFA preferably has from 92 to 99 mol % of the units of TFE,and from 1 to 8 mol % of the units of PAVE, to all units, whereby a rollfilm which is excellent in the dimensional stability and which has apredetermined thickness can be obtained.

The fluororesin is preferably a fluororesin (hereinafter referred toalso as “fluororesin i”) having a functional group (hereinafter referredto also as “functional group i”) having an ion scavengering function.

The functional group i is a functional group having a function ofscavengering ionic substances, when annealing treatment is carried outat a temperature of at least 80° C. and at most 300° C. It is consideredthat the main factor of the electrolytic corrosion phenomenon iscorrosion phenomenon. The corrosion phenomenon results, since ionsgenerated by electrochemical reactions or deterioration of materials forforming a circuit, or ionic substances (hydrogen chloride in air, dustshaving NOx, SOx or the like adsorbed, deposits such as an oil component,countercations derived from various additives contained in otherboard-constituting materials such as soldering flux or an insulatingadhesive layer) incorporated from outside by surface adhesion or thelike move by migration or electric force and electrochemically react ona surface of a substance having an electrode function. It is consideredthat the functional group i reacts with the ionic substances which maycause electrolytic corrosion and fixes or inactivates the unnecessaryionic substance.

The functional group i is preferably at least one member selected fromthe group consisting of a carbonyl group, a carboxy group, a carboxylicacid anhydride group (—C(═O)—O—C(═O)—), a carboxylate group, a sulfonylgroup, a sulfo group and a sulfonic acid anhydride group(—S(═O)₂—O—S(═O)₂—) from the viewpoint of the ion scavengering functionand thermal stability, and is particularly preferably a carboxy group, acarboxylic acid anhydride group or a carboxylate group, which is notionized.

The functional group i in the fluororesin i may be derived from amonomer having the functional group i, may be derived from apolymerization initiator or a chain transfer agent or may be derivedfrom a compound having the functional group i graft-polymerized to thefluororesin.

The monomer having the functional group i may, for example be a cyclicmonomer having the after-mentioned carboxylic acid anhydride group, aperfluoro[2-(fluorosulfonylethoxy)propyl vinyl ether] ormethylperfluoro-5-oxy-6-heptanoate (hereinafter referred to also as“MXM”).

The content of the functional group i in the fluororesin i is preferablyfrom 10 to 60,000 groups, more preferably from 300 to 5,000 groups, per1×10⁶ carbon atoms of the main chain of the fluororesin i, from theviewpoint of the melting temperature of the fluororesin i. In such acase, the balance among the stability in the electrolytic corrosion testof a copper-clad laminate produced by using a roll film as in the formof a printed board, the adhesion between the roll film to be unwound anda copper layer and the heat resistance, the mechanical property and theelectric characteristics of the roll film will be good.

The content of the functional group i can be measured by a method suchas nuclear magnetic resonance analysis or infrared absorption spectrumanalysis and can, for example, be calculated from the proportion (mol %)of units having the functional group i to all units of the fluororesin iby the method described in JP-A-2007-314720.

As the fluororesin i, a fluororesin having units having the functionalgroup i or a terminal group having the functional group i may bementioned. As specific examples, a melt-processablepolytetrafluoroethylene having the functional group i, PFA having thefunctional group i, FEP having the functional group i, an ethylene/TFEtype copolymer (ETFE) having the functional group i, aTFE/perfluoro[2-(fluorosulfonylethoxy)prolyl vinyl ether] type copolymer(e.g. Nafion manufactured by Dupont), and a TFE/MXM copolymer and anacid type exchanged resin thereof (e.g. Flemion, manufactured by AGCInc.) may be mentioned. The fluororesin i may be a mixture of two ormore types. Here, “type” in the above copolymers means that thecopolymers may further have units of another monomer.

The fluororesin i is preferably PFA having the functional group i, FEPhaving the functional group i or the TFE/MXM polymer with a view tosatisfying both the content of fluorine and processability.

The fluororesin i is preferably a fluororesin having units having thefunctional group i. In such a case, the ion scavengering function andthe adhesion to various substrates such as a metal foil tend to befurther improved.

The fluororesin is preferably a fluororesin (hereinafter referred toalso as “fluororesin ii”) having units u1 of TFE or CTFE, units u2 of acyclic monomer having a carboxylic acid anhydride group or MXM and unitsu3 of a fluorinated monomer, since the adhesion at an interface betweenan unwound roll film and a copper layer and the electric characteristicsof a roll film will be further excellent.

The monomer constituting the units u1 is preferably TFE, since the heatresistance will be excellent.

The cyclic monomer may, for example, be itaconic acid anhydride (IAH),citraconic acid anhydride (CAH), 5-norbornene-2,3-dicarboxylic acidanhydride (NAH) or maleic acid anhydride. As the cyclic monomer, onetype may be used alone, or two or more types may be used in combination.

The cyclic monomer is preferably IAH, CAH and NAH, and from theviewpoint of further excellent adhesion, IAH and NAH are preferred.

The fluororesin ii may have units having a dicarboxylic group (such asitaconic acid, citraconic acid, 5-norbornene-2,3-dicarboxylic acid ormaleic acid) formed by hydrolysis of a part of the carboxylic acidanhydride group in the units u2 in some cases. In such a case, thecontent of the above units is included in the content of the units u2.

The fluorinated monomer constituting the units u3 may, for example, be afluoroolefin (such as VF, VDF, CF₂═CHF, HFP or hexafluoroisobutylene)other than TFE and CTFE, PAVE, CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F,CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₃H, CF₂═CFCF₂OCF═CF₂, CF₂═CFCF₂CF₂OCF═CF₂, afluoroalkylethylene (FAE), perfluoro(2,2-dimethyl-1,3-dioxol),2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxol orperfluoro(2-methylene-4-methyl-1,3-dioxolane).

The fluorinated monomer is a fluorinated monomer other than TFE andCTFE, and is preferably at least one member selected from the groupconsisting of HFP, PAVE and FAE, particularly preferably PAVE in view ofexcellent processability of the fluororesin ii and the flex resistanceof a roll film.

As PAVE, CF₂═CFOCF₂CF₃, CF₂═CFOCF₂CF₂CF₃ (PPVE), CF₂═CFOCF₂CF₂CF₂CF₃ andCF₂═CFO(CF₂)₈F may be mentioned, and PPVE is preferred.

As FAE, CH₂═CF(CF₂)₂F, CH₂═CF(CF₂)₃F, CH₂═CF(CF₂)₄F, CH₂═CF(CF₂)₅F,CH₂═CF(CF₂)₈F, CH₂═CF(CF₂)₂H, CH₂═CF(CF₂)₃H, CH₂═CF(CF₂)₄H, CH₂═CF(CF₂H,CH₂═CF(CF₂)₈H, CH₂═CH(CF₂)₂F, CH₂═CH(CF₂)₃F, CH₂═CH(CF₂)₄F,CH₂═CH(CF₂)₅F, CH₂═CH(CF₂)₆F, CH₂═CH(CF₂)₅F, CH₂═CH(CF₂)₂H,CH₂═CH(CF₂)₃H, CH₂═CH(CF₂)₄H, CH₂═CH(CF₂)₅H, CH₂═CH(CF₂)₅H, etc. may bementioned, and CH₂═CH(CF₂)₄F(PFBE) and CH₂═CH(CF₂)₂F(PFEE) arepreferred.

The preferred proportions of respective units to the total amount of theunits u1, the units u2 and the units u3 in the fluororesin ii are asdescribed below from the viewpoint of the flame resistance, the chemicalresistance, etc. of a roll film.

The proportion of the units u1 is preferably from 90 to 99.89 mol %,more preferably from 95 to 99.47 mol %, further preferably from 96 to98.95 mol %.

The proportion of the units u2 is preferably from 0.01 to 3 mol %, morepreferably from 0.03 to 2 mol %, further preferably from 0.05 to 1 mol%. In a case of such a fluororesin ii, the adhesion at an interfacebetween an unwound roll film and a copper layer will be furtherexcellent.

The proportion of the units u3 is preferably from 0.1 to 9.99 mol %,more preferably from 0.5 to 9.97 mol %, further preferably from 1 to9.95 mol %. In such a case, the processability of the fluororesin ii,the flex resistance of a roll film, etc. will be further excellent.

The proportion of the respective units can be calculated by melt NMRanalysis, fluorine content analysis, infrared absorption spectrumanalysis, etc. of the fluororesin

The fluororesin ii may further have units u4 of another monomer.

Such another monomer may, for example, be an olefin (such as ethylene,propylene or 1-butene) or a vinyl ester (such as vinyl acetate). Asanother monomer, one type may be used alone, or two or more types may beused in combination. Such another monomer is preferably ethylene,propylene or 1-butene, particularly preferably ethylene, from theviewpoint of the mechanical strength of a roll film, etc.

As specific examples of the fluororesin ii, a TFE/NAH/PPVE copolymer, aTFE/IAH/PPVE copolymer, a TFE/CAH/PPVE copolymer, a TFE/IAH/HFPcopolymer, a TFE/CAH/HFP copolymer, a TFE/IAH/PFBE/ethylene copolymer, aTFE/CAH/PFBE/ethylene copolymer, a TFE/IAH/PFEE/ethylene copolymer, aTFE/CAH/P FEE/ethylene copolymer and a TFE/IAH/HFP/PFBE/ethylenecopolymer may be mentioned.

The fluororesin ii is preferably PFA having the functional group i, morepreferably PFA having units having the functional group i, particularlypreferably a TFE/NAH/PPVE copolymer, a TFE/IAH/PPVE copolymer or aTFE/CAH/PPVE copolymer.

The roll film of the present invention comprises the fluororesin as themain component, and its content is preferably from 50 to 100 mass %,more preferably from 80 to 100 mass %. The roll film may further containa resin other than the fluororesin, an additive or the like. Further,components used for producing the fluororesin (such as a surfactant forthe polymerization) are not included in other components.

Other resin may, for example, be a non-melt-processable fluororesin, afluorinated elastomer or a resin containing no fluorine atom.

The fluorinated elastomer is preferably an elastomer having units of atleast one fluoroolefin selected from the group consisting of TFE, HFP,VDF and CTFE. Specifically, the TFE/propylene type copolymer mentionedin JP-A-H05-78539, the VDF/HFP copolymer, the VDF/HFP/TFE copolymer,etc. mentioned in JP-A-H11-124482, and the fluorinated polymer havingunits of TFE and having units of CF₂═CFOCF₃ mentioned inJP-A-2006-089720, etc. may be mentioned. These polymers may further haveunits of another monomer.

The resin having no fluorine atom may, for example, be a polyester, apolyolefin, a styrene type resin, a urethane resin, a polyoxymethylene,a polyamide, a polycarbonate, a polymethyl methacrylate, a polyvinylchloride, a polyphenylene sulfide, polyphenylene ether, a modifiedpolyphenylene ether, a polyimide, a polyamideimide, a polyether imide, apolysulfone, a modified polysulfone, a polyethersulfone, a polyketone, apolyether ketone, a polyether ether ketone, a polyether ketone ketone, apolyarylate, a polyether nitrile, a phenol resin, a phenoxy resin or anepoxy resin.

The additive may, for example, be an inorganic filler or an organicfiller.

The inorganic filler may, for example, be silica, hollow silica, clay,talc, calcium carbonate, mica, diatomaceous earth, alumina, zinc oxide,titanium oxide, calcium oxide, magnesium oxide, iron oxide, tin oxide,antimony oxide, calcium hydroxide, magnesium hydroxide, aluminumhydroxide, basic magnesium carbonate, magnesium carbonate, zinccarbonate, barium carbonate, dawsonite, hydrotalcite, calcium sulfate,barium sulfate, calcium silicate, montmorillonite, bentonite, activatedwhite clay, sepiolite, imogolite, sericite, glass fibers, glass beads,silica balloons, carbon black, carbon nanotubes, carbon nanohorns,graphite, carbon fibers, glass balloons, carbon balloons, wood flower orzinc borate. The inorganic filler may be porous or non-porous. Theinorganic filler may be subjected to surface treatment with a surfacetreatment agent such as a silane coupling agent or a titanate couplingagent for improving the dispersibility in the resin. As the inorganicfiller, one type may be used alone, or two or more types may be used incombination.

The organic filler is preferably a particulate filler containing otherresin as the main component, particularly preferably a particulatefiller made of a material having a low dielectric property, and aparticulate filler of PTFE, a polystyrene or a polyolefin, a hollowfiller of such a resin, etc. may be mentioned.

The fluororesin for a roll film may be one type of a fluororesin or maybe two or more types of fluororesins. As a specific example of thelatter case, an embodiment comprising the fluororesin i and afluororesin other than the fluororesin i may be mentioned.

In the above embodiment, the fluororesin i is preferably the fluororesinii, and the fluororesin other the fluororesin i is preferably PFA havingno functional group i.

In the above embodiment, the proportion of the fluororesin i ispreferably from 0.1 to 49 mass %, more preferably from 5 to 40 mass %,to the total amount of fluororesins in a roll film. The proportion ofthe fluororesin other than the fluororesin i is preferably from 51 to99.9 mass %, more preferably from 60 to 95 mass %.

The roll film may consist of only a film of the fluororesin or may beformed on a surface of other substrate. In the former case, the rollfilm may consist of a film having one layer of the fluororesin or mayconsist of a film having two or more layers of the fluororesin. In thelatter case, as other substrate, a film of a fluororesin may be used.

The thickness of the roll film of the present invention is from 1 to 100μm, more preferably from 3 to 75 μm, particularly preferably from 3 to50 μm. When the thickness of the roll film is at least the lower limitvalue of the above range, the forming property of the copper-cladlaminate is excellent. When the thickness of the roll film is at mostthe upper limit value of the above range, a thin printed board can beformed, and the multi-layer forming property is excellent. As a furtherspecific embodiment of the thickness of the roll film, a thin filmembodiment of from 3 to 30 μm and a thick film embodiment of from 30 to60 μm may be mentioned.

In the roll film of the present invention, the dimensional change rate,in terms of an absolute value, in each of MD and TD is less than 1.0%,when heated at 150° C. for 30 minutes and then cooled to 25° C., basedon the dimension at 25° C. Hereinafter, the former absolute value isreferred to also as “change rate MD”, and the latter absolute value isreferred to as “change rate TD”.

Roll films made of conventional melt-processable fluororesins haveresidual forming strain due to its production method (melt molding byextrusion or the like). The dimensional change rate of such roll filmsthereby exceeds 1.0%. Under such circumstances, in the presentinvention, the dimensional change rate of a roll film in each of MD andTD is suppressed within a predetermined range, and the electrolyticcorrosion is suppressed, by controlling the thickness of the film of afluororesin and the after-mentioned annealing treatment conditions andwinding conditions of the film. Accordingly, a high-precisioncopper-clad laminate can be obtained by unwinding the roll film of thepresent invention and forming a copper layer thereon, and a printedboard of which electrolytic corrosion is suppressed can be obtained.

The change rate MD is preferably less than 0.5%, preferably at most0.1%, more preferably at most 0.08%, particularly preferably at most0.05%.

The change rate TD is preferably less than 0.5%, preferably at most0.1%, more preferably at most 0.08%, particularly preferably at most0.05%.

In the roll film of the present invention, the ratio of winding tensionto the change rate MD is preferably from 100 to 1,000,000, particularlypreferably from 300 to 10,000. In such a case, the dimensional stabilityof the roll film tends to further improve.

Further, the ratio of the change rate MD to the change rate TD ispreferably at most 5, particularly preferably at most 3. In such a case,if the roll film is long, a more high-precision printed board can beproduced. The lower limit of the above ratio is usually 1.

The relative dielectric constant of the roll film is preferably at most3.0, more preferably at most 2.5, particularly preferably at most 2.2.The lower limit of the relative dielectric constant is, for example,1.8. In such a case, the transmission efficiency of a printed board tobe obtained from the roll film will be further excellent.

The roll film of the present invention is used for a copper-cladlaminate. Specifically, the roll film is unwound and laminated with acopper layer to form a copper-clad laminate.

According to the above-described roll film, a printed board excellent inthe stability in the electrolytic corrosion test can be obtained fromthe copper-clad laminate in which the roll film is used.

Further, when the fluororesin has the functional group i, the adhesionbetween the roll film and the copper layer will be improved.

Further, it is considered that the main factor of the electrolyticcorrosion phenomenon is corrosion phenomenon due to ionic substances.

When the fluororesin has the functional group i, the ionic substancesare fixed or inactivated by the functional group i, whereby a printedboard more excellent in the stability in the electrolytic corrosion testcan be obtained Further, the functional group i chemically bonds to themain chain of the fluororesin, whereby the mobility of the functionalgroup i in a film is low, as compared with a case where a fluororesincontains a low molecular material having the functional group i. It isthereby considered that electric field generated at the time of applyingelectrical current to a circuit, ionic conduction due to magnetic fieldor the like, diffusion, etc. can be suppressed, whereby the effect offixing or inactivating ionic substances is high.

In the method for producing a roll film of the present invention, a filmcomprising a fluororesin as the main component and having a thickness offrom 1 to 100 μm (hereinafter referred to also as “untreated film”) issubjected to annealing treatment at a temperature of from a temperaturelower by 210° C. than the melting temperature (hereinafter referred toalso as “Tm”) of the fluororesin to a temperature lower by 20° C. thanTm, and the film is wound.

The untreated film has each of change rate MD and change rate TD ofhigher than 1.0%, typically each of higher than 1.0% and at most 5%.

The specific temperature for the annealing treatment is at least (glasstransition temperature of the fluororesin+10° C.) and at most (themelting temperature of the fluororesin−20° C.), and in the case ofnormal fluororesins (PFA having a melting temperature of from 260 to320° C., etc.), it is from 80 to 300° C.

In the annealing treatment, tension is preferably applied toward MD of afilm. The tension at that time is preferably at most 10 N/m,particularly preferably at most 5 N/m. The lower limit of the tension atthat time is usually 1 N/m.

When winding an anneal-treated film, tension (hereinafter referred toalso as “winding tension”) is preferably applied toward MD of the film.The winding tension is preferably at most 500 N/m, more preferably atmost 300 N/m, particularly preferably at most 150 N/m. The lower limitof the tension at that time is usually 1 N/m. Further, the ratio of thewinding tension to the change rate MD in terms of an absolute value ispreferably from 100 to 1,000,000, particularly preferably from 300 to10,000.

Here, each tension (N/m) is a value per MD 1 m of the film and, in anactual film treatment apparatus, it is obtained from tension measured bya film tension measuring apparatus and a film width (m) at that time.Such a film tension measuring apparatus may, for example, be trade name“Model 1FB-5000N” and “Model HD-500”, manufactured by OHKURA INDUSTRY ora non-contact WEB tension meter, manufactured by Bellmatic. The windingtension is measured by installing a winding roll with a 3 inch ABSplastic tube (thickness of 6 mm) connected to such a measuringapparatus.

An example of the method for producing an untreated film will bedescribed with reference to FIG. 1.

FIG. 1 is a view schematically illustrating an example of an untreatedfilm production apparatus 100.

The production apparatus 100 has an extruder 101, a T die 102 installedto the extruder 101, a quenching roll 103, a plurality of cooling rolls104, a pair of nip rolls 105 and a winding roll 106.

The plurality of cooling rolls 104 are installed in series so that afilm form melt 11 discharged from the T die 102 will sequentially passthe plurality of cooling rolls 104 toward the side of the pair of niprolls 105. Here, three cooling rolls 104 are illustrated, however, thenumber of the cooling rolls 104 is not limited to three and may be one.

The quenching roll 103 is installed opposite to the cooling roll 104(hereinafter referred to also as “first quenching roll”) which is thenearest to the T die 102 among the plurality of cooling rolls 104.

The untreated film is produced by the production apparatus 100 by thefollowing procedure.

A material containing a fluororesin and as a case requires, a resinother than the fluororesin, an additive, etc. is melted by the extruder101, the molten resin extruded from the extruder 101 is supplied to theT die 102, the molten resin is discharged from the T die 102 into a filmform, the film-form melt 11 is pressed on the first cooling roll 104 bythe quenching roll 103 and then brought into contact with the othercooling rolls 104 sequentially and thereby cooled, and conveyed so as topass through the pair of nip rolls 105, whereby an untreated film 12 isformed. The obtained untreated film 12 is wound on the winding roll 106.As a case requires, the untreated film 12 may be cut into sheets.

The rip width of the T die 102 is not particularly restricted and may,for example, be from 500 to 4,000 mm.

The forming rate, that is discharge rate of the melt 11 from the T die102, is preferably from 1 to 100 m/min, particularly preferably from 1to 30 m/min. When the forming rate falls within the above range, thefilm flatness is excellent. When the forming rate is lower than thelower limit value of the above range, the melt 11 is cooled before beingbrought into contact with the cooling roll, whereby the film flatnessmay deteriorate. When the forming rate exceeds the upper limit value ofthe above range, film cooling is delayed, whereby the film flatness maydeteriorate.

The distance from the discharge of the melt 11 from the T die 102 to thecontact point of the first cooling roll 104 is preferably at most 500mm, particularly preferably at most 300 mm. The lower limit of the abovedistance is, for example, 100 mm.

The surface temperature of the cooling roll 104 is less than Tm of theresin material and preferably at least room temperature and at most(Tm−20° C.).

The surface temperature of the quenching roll 103 may be the same as thesurface temperature of the cooing roll 104.

In the above production method, the melt 11 is pressed on the firstcooling roll 104 by the quenching roll 103, whereby the change rate MDat the time of the annealing treatment is low, whereby the change rateMD in terms of an absolute value can be suppressed under mild annealingtreatment conditions. This is considered that the melt 11 is quenched,whereby the forming strain at film terminals is suppressed, and theuniformity of the strain in MD of the film is high.

Here, in the above production method, the melt 11 may be cooled withoutbeing pressed by the quenching roll 103.

When the fluororesin is the fluororesin i, ionic substances which maycause corrosion will be sufficiently fixed or inactivated by thefunctional group i, when heated in annealing treatment, whereby aprinted board which is excellent in the stability in the electrolyticcorrosion test tends to be obtained from the roll film. Further, thefilm-form retention property when annealed is also excellent.

The time for the annealing treatment may be appropriately setconsidering the desired dimensional change rate of the roll film and thetemperature of the annealing treatment. The time for the annealingtreatment is preferably from 1 to 60 minutes, particularly preferablyfrom 1 to 30 minutes. When the annealing time is at least the lowerlimit value of the above range, a printed board which is excellent inthe stability in the electrolytic corrosion test tends to be obtainedfrom the roll film. When the annealing time is at most the upper limitvalue of the above range, the treatment efficiency is high, and aprinted board can be industrially easily produced.

The annealing treatment is preferably carried out while applying tensionto the untreated film. As such an embodiment, an example that anuntreated film in the form of a roll is heated while being conveyed inMD by roll-to-roll processing, may be mentioned.

Tension applied to the untreated film in the annealing treatment ispreferably at most 10 N/m, particularly preferably at most 5 N/m. Whenthe tension is at most the above upper limit value, stress applied tothe untreated film is low, and remaining stress in a roll film canthereby be reduced. When the remaining stress in the roll film is low,the dimensional stability of the roll film will be more excellent.

In a case where the untreated film is heated while being conveyed in MDby a roll to roll, tension (hereinafter referred to also as “conveyancetension”) applied to the untreated film at the time of conveyance ispreferably at least 1 N/m in a region heated for the annealingtreatment. When the conveyance tension is at least the above lower limitvalue, the film can be stably conveyed.

In a case where the annealing treatment is carried out under applyingtension to the untreated film, it is preferred that another substrate islaminated on the untreated film prior to the annealing treatment, andthe annealing treatment is carried out under a state laminated with thesubstrate. Stress applied to the untreated film can be thereby easilycontrolled.

Another substrate may, for example, be a resin film.

The resin constituting the resin film may, for example, be amelt-processable fluororesin, a non-melt-processable fluororesin or anon-fluororesin. The non-fluororesin may, for example, be a polyesterresin (such as a polyethylene terephthalate (PET) resin, a polyethylenenaphthalate resin (PEN), etc.) or a polyimide resin.

The resin film is preferably a film of a fluororesin, since thecoefficient of linear expansion of the untreated film is close to thatof another substrate, and curling is less likely to be formed in theannealing treatment. The fluororesin constituting the film of thefluororesin is preferably a fluororesin of the same type as thefluororesin contained in the untreated film, since the linear expansioncoefficient of the untreated film is close to that of the substrate, andcurling is less likely to be formed in the annealing treatment. Forexample, in a case where the fluororesin is PFA, the resin constitutingthe resin film is preferably PFA. The fluororesin constituting the resinfilm may have no functional group i.

The thickness of the substrate is preferably from 25 to 100 μm.

The substrate may be directly laminated on the untreated film or may belaminated via an adhesive layer.

A laminate having the substrate directly laminated on the untreated filmmay, for example, be produced, in the above production method, bycoextruding a resin material containing a melt-processable fluororesinand a resin material constituting a substrate film. Feed-block method ormulti-manifold method can be employed in the above coextrusion process.

In a case where the substrate is laminated on the untreated film via anadhesive layer, an adhesive constituting the adhesive layer is notparticularly restricted and may, for example, be an acrylic type, asilicone type, a urethane type or a polyolefin type.

The thickness of the adhesive layer is preferably from 0.1 to 5 μm,particularly preferably from 0.5 to 2 μm.

Now, with reference to FIGS. 2 and 3, an example of the method forproducing a roll film of the present invention will be described. FIG. 2is a view illustrating an example of a schematic structure of a bondingapparatus for bonding an untreated film and a substrate. FIG. 3 is aview illustrating an example of a schematic structure of an annealingtreatment apparatus.

The bonding apparatus 200 illustrated in FIG. 2 has a first unwindingroll 201 to sequentially unwind an untreated film 12 in a roll form, asecond unwinding roll 202 to sequentially unwind a substrate 13 havingan adhesive layer, which is wound in a roll form, a pair of bondingrolls 203 and 204 to bond the untreated film 12 and the substrate 13having an adhesive layer thereby to form a laminate 14 and a windingroll 205 to wind the laminate 14.

The untreated film 12 and the substrate 13 having an adhesive layer aresandwiched by and pressed between the pair of bonding rolls 203 ad 204and thereby bonded.

The substrate 13 having an adhesive layer has an adhesive layer on onesurface of the substrate, specifically on a surface at a side being incontact with the untreated film 12 when the substrate passes through thebonding roll 203.

The annealing treatment apparatus 300 illustrated in FIG. 3 has anunwinding roll 301 to sequentially unwind a laminate 14 wound in a filmform, a heating portion 302 to heat the laminate 14, a plurality ofconveying rolls 303 and a winding roll 304 to wind the heated laminate14, that is a laminate 15 having a roll film and a substrate 13 havingan adhesive layer.

The heating portion 302 has a space S into which the laminate 14 isconveyed, and the plurality of conveying rolls 303 are installed in thespace S. Further, the heating portion 302 has a heating structure (notillustrated) to heat the laminate 14 conveyed into the space S.

In the annealing treatment apparatus 300, the unwinding rate and thewinding rate of the laminate 14 are controlled by the unwinding roll 301and the winding roll 304, whereby conveyance tension and winding tensionapplied to the laminate 14 being conveyed can be controlled.

In this example of the production method, a roll film is produced by thefollowing procedure.

First, in the bonding apparatus 200, the untreated film 12 is conveyedfrom the first unwinding roll 201 to the bonding rolls 203 and 204, thesubstrate 13 having an adhesive layer is conveyed from the secondunwinding roll 202 to the bonding rolls 203 and 204, the untreated film12 and the substrate 13 having an adhesive layer are bonded by thebonding rolls 203 and 204, and the obtained laminate 14 is wound on thewinding roll 205.

Next, the wound laminate 14 is transferred to the unwinding roll 301 inthe annealing treatment apparatus 300, conveyed from the unwinding roll301 to the heating portion 302 and heated at the heating portion 302, toform the untreated film 12 into a roll film, and a laminate 15 havingthe roll film and the substrate 13 having an adhesive layer is wound onthe winding roll 304. As a case requires, the laminate 15 may be cutinto sheets. As a case requires, the substrate 13 having an adhesivelayer may be peeled from the laminate 15. The substrate 13 having anadhesive layer is usually peeled at the time of producing a copper-cladlaminate.

A copper-clad laminate formed by using the roll film of the presentinvention has a dielectric layer made of an unwound roll film and acopper layer formed so as to be in contact with the dielectric layer.

FIG. 4 is a cross-sectional view schematically illustrating an exampleof a copper-clad laminate. A copper-clad laminate 40 illustrated in FIG.4 has a dielectric layer 41 consisting of an unwound roll film, and acopper layer 42 laminated on a first surface 41 a in the thicknessdirection of the dielectric layer 41.

FIG. 5 is a cross-sectional view schematically illustrating anotherexample of a copper-clad laminate. A copper-clad laminate 50 illustratedin FIG. 5 has a dielectric layer 51 consisting of an unwound roll film,a first copper layer 52 laminated on a first surface 51 a in thethickness direction of the dielectric layer 51 and a second copper layer53 laminated on a second surface 51 b on the side opposite from thefirst surface 51 a of the dielectric layer 51.

The thickness of the copper layer is preferably from 3 to 18 μm. In acase where a fine circuit is formed, the thickness of the copper layeris preferably at most 12 μm.

The copper layer is preferably formed by using a copper foil. The copperfoil may, for example, be a rolled copper foil or an electrolytic copperfoil.

In the method for producing a copper-clad laminate of the presentinvention, the roll film of the present invention (or a film productmanufactured by its production method) is unwound, and a copper layer isformed on its surface.

The copper layer may be formed on only a first surface in the thicknessdirection of the roll film, or on both the first surface and the secondsurface on the side opposite from the first surface.

The method for forming the copper layer on a surface of the unwound rollfilm may, for example, a method of laminating (bonding) a copper foil ona surfaces of the roll film, a vapor deposition method or a platingmethod.

The method for laminating a copper foil may, for example, be a method ofhot press. The hot press temperature is preferably from the meltingpoint of the dielectric film+20° C. to the melting point of thedielectric film+100° C. The hot press time may, for example, be from 1to 30 minutes. The hot press pressure may, for example, be from 0.1 to10 MPa.

The unwound roll film is preferably subjected to surface treatmentbefore forming the copper layer in order to improve the adhesive betweenthe copper layer and the unwound roll film. The surface treatment may,for example, be plasma treatment, corona treatment and ultraviolet ray(UV) application.

The obtained copper-clad laminate can be used as a material for aprinted board.

The printed board is a plate component to electrically connectelectronic components such as a semiconductor and a condenser chip andsimultaneously to fix them in a limited space.

The construction of a printed board to be formed from the copper-cladlaminate is not particularly restricted, and a known construction of aprinted board may be employed. The printed board may be any one of arigid board, a flexible board or a rigid flexible board. The printedboard may be a single-side board, a double-side board or a multi-layerboard (such as a buildup board).

In the method for producing a printed board of the present invention,the copper-clad laminate is produced by the above method for producing acopper-clad laminate, and the copper layer is etched to form a patternedcircuit.

As the etching method of the copper layer, a known method may beemployed.

In the production of a printed board, after etching the copper layer toform a patterned circuit, an interlayer insulation film may be formed onthe patterned circuit, and a patterned circuit may be further formed onthe interlayer insulation film.

In the production of a printed board, a solder resist may be laminatedon the patterned circuit.

In the production of a printed board, a cover lay film may be laminated.The cover lay film typically comprises a substrate film and an adhesivelayer formed on a surface of the substrate film, and a surface of theadhesive layer is bonded to a printed board.

A board obtained by etching the copper layer of the copper-clad laminatemay be used as an inner circuit board to produce a buildup board.

A printed board to be obtained by the method for producing a printedboard of the present invention may be used for various electricappliances and systems. Particularly, the printed board is useful as aboard for electronics required to have high frequency properties such asa radar, a router for a network, a backplane or wireless infrastructure,a board for various sensors for automobiles or a board for an enginemanagement sensor, and suitable in applications for reducingtransmission loss in millimeter wave ranges.

EXAMPLES

Now, the present invention will be described with reference to Examples,but the present invention is not limited by the following description.

The measuring or test methods employed in each Ex. and materials will bedescribed below.

(Measuring Method)

<MFR [g/10 min]>

The mass (g) of a fluororesin discharged from a nozzle having a diameterof 2 mm and a length of 8 mm for 10 minutes at 372° C. under a load of49N was measured by means of a melt indexer (manufactured by TECHNOLSEVEN CO., LTD.).

<Thickness>

The thickness was obtained by means of a contact type thickness meterOG-525H (manufactured by ONO SOKKI Co., Ltd.) with a gauge head AA-026(φ10 mm SR7).

<Dimensional Change Rate [%]>

A sample was prepared by cutting a film into a length (MD) 12 cm×width(TD) 12 cm, and the dimensional change rate was obtained by thefollowing method.

A straight line having a length of about 10 cm was drawn on the samplealong each direction of MD and TD at 25° C., and the distance betweenterminal points of each liner was taken as initial length L₀. Then, thesample was subjected to heat treatment at 150° C. for 30 minutes andcooled to 25° C., and the straight line distance L₁ between the terminalpoints of the straight line drawn on the sample was measured to obtain adimensional change rate (%) by the following formula 1.

Dimensional change rate (%)=(L ₁ /L ₀−1)×100  formula 1

The dimensional change rate obtained with respect to the straight linealong MD is taken as the dimensional change rate of MD (change rate MD),in terms of an absolute value, and the dimensional change rate obtainedwith respect to the straight line along TD is taken as the dimensionalchange rate of TD (change rate TD), in terms of an absolute value.

<Peeling Test>

A produced copper layer laminate was cut into a width of 1 cm to preparean evaluation sample. The dielectric film and the copper foil wereseparated from one end in the length direction of the evaluation sampleto a position of 50 mm. Then, they were peeled by means of a tensiletester at room temperature at a pulling rate of 100 mm/min at 90°, andthe average load from a measuring distance of 20 mm to 80 mm was takenas a peel strength (N/cm). The room temperature was 25° C.

<Electrolytic Corrosion Test>

The electrolytic corrosion test was carried out in accordance with asimplified electrolytic corrosion evaluation method described in “HighInsulation Reliability of Glass Cloth Based Copper Clad Laminates”,Circuit Technology Vol. 3, No. 4, p 212-219 (1988).

In the electrolytic corrosion test, a pattern having two comb patterns60 in combination illustrated in FIG. 6 is used. Each comb pattern 60has a plurality of line parts 61 arranged in parallel and a base part 62extending in a direction orthogonal to the length direction of the lineparts 61 and connecting to the respective line parts 61. In the abovepattern, a plurality of line parts 61 of one comb pattern 60 and aplurality of line parts 61 of the other comb pattern 60 arealternatively arranged in a direction orthogonal to the length directionof the line parts 61, and the respective comb patterns 60 are not incontact with each other. In each comb pattern 60, the length of the lineparts 61 is 100 mm, the width of the line parts 61 is 0.33 mm, and thenumber of the line parts 61 is 100. The interval between adjacent lineparts 61 is 0.10 mm.

A copper layer of a produced copper-clad laminate was etched to form twocomb patterns illustrated in FIG. 6 and retained by means of a universalthermo-hygrostat oven (PL-1KTH, manufactured by TABAIESPEC) under aconstant temperature and humidity condition of 85° C. and 85% RH for atreatment time of 500 hours to obtain a sample 71.

As illustrated in FIG. 7, the two comb patterns of the sample 71 wereconnected to a positive terminal and a negative terminal of a powersource 72 respectively, and the sample 71 was dipped in an electrolyte L(1 μmol/L HCl aqueous solution), and voltage was applied. Appliedcurrent was 20 VDC, and application time was 100 minutes. Then, thesample 71 was taken out from the electrolyte L, and AC resistance value(Ω·cm) between the two comb patterns was measured under conditions of 10Hz and 1 A.

The stability in the electrolytic corrosion test was evaluated from themeasured AC resistance value based on the following standard. If the twocomb patterns contact each other due to deformation or the like, the ACresistant value is low. The higher the AC resistant value is, the betterthe stability in the electrolytic corrosion test is.

◯ (good): AC resistant value exceeds 10⁻⁹ Ω·cm.

x (bad): AC resistant value is at most 10⁻⁹ Ω·cm.

<Used Materials>

PFA1: PFA synthesized in the same manner as in WO2016/017801, paragraph[0124]. The proportion of the respective units isTFE/NAH/PPVE=97.9/0.1/2.0 mol %. This PFA has a carboxylic acidanhydride group as the functional group i. The content of the carboxylicacid anhydride group is 1,000 per 1×10⁶ carbon atoms of the main chain,the melting temperature is 300° C., and the melt flow rate is 17.0 g/10min.

PFA2: “P-63P” manufactured by Asahi Glass Company, Limited, which is PFA(MFR: 15.0 g/10 min) having no functional group i.

PFA3: “P-62XP” manufactured by Asahi Glass Company, Limited, which isPFA (MFR: 25.0 g/10 min) having no functional group i.

ETFE1: “C88AX” manufactured by Asahi Glass Company, Limited, which isETFE (MFR: 15 g/10 min) having no functional group i.

Copper foil: “CF-T4X-SVR” manufactured by Fukuda Metal Foil & PowderCo., Ltd., electrolytic copper foil, thickness 12 μm.

Ex. 1

Pellets of PFA1 were extruded into a film form by means of a 65 mmφsingle screw extruder (manufactured by Toshiba Machine Co., Ltd.,L/D=25, compression ratio of 3.1) having a T die having a width of 700mm at a forming temperature of 340° C. at a forming rate of 3.5 m/min toobtain a film (untreated film wound in a roll form) having a thicknessof 50 μm and a width of 510 mm.

The film was unwound from an unwinding roll 301 by means of an annealingtreatment apparatus 300 having the construction illustrated in FIG. 3,conveyed to a heating portion 302 with a tension of 5 N/m, heated at theheating portion 302 under conditions of 150° C. and 5 minutes and woundon a winding roll 304 with a tension of 62.5 N/m to obtain a roll filmhaving a thickness of 50 μm. That is, the annealing treatment conditionswere the temperature of 150° C., time of 5 minutes and conveyancetension of 5 N/m, and the winding condition was winding tension of 62.5N/m.

The obtained roll film was unwound and cut into a length of 15 cm×widthof 15 cm, and a copper foil having the same size was placed on onesurface, followed by hot press by means of a vacuum pressing machineunder conditions of 340° C., 15 minutes and 1.5 MPa to obtain acopper-clad laminate.

The obtained copper-clad laminate was subjected to the peeling test andthe electrolytic corrosion test. The results are shown in Table 1.

Ex. 2 to 14

A roll film was obtained in the same manner as in Ex. 1, except that thetype of the fluororesin, the forming conditions, the annealing treatmentconditions by roll-to-roll process and the winding conditions werechanged as shown in Table 1, and a copper-clad laminate was produced andsubjected to the peeling test and electrolytic corrosion test. Theresults are shown in Table 1.

TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Type of fluororesinPFA1 PFA1 PFA1 PFA1 PFA1 PFA1 PFA1 Molding condition Die width [mm] 700700 1,900 1,900 1,900 1,900 1,900 Forming rate [m/min] 3.5 3.5 10 10 1010 10 Annealing treatment conditions Temperature [° C.] 150 150 150 150150 150 240 Time [min] 5 5 5 15 5 5 5 Tension [N/m] 5 10 5 10 5 5 5Winding conditions [N/m] Tension [N/m] 62.5 125 62.5 62.5 31.3 300 62.5Roll film physical properties Construction Monolayer Monolayer MonolayerMonolayer Monolayer Monolayer Monolayer film film film film film filmfilm Thickness [μm] 50 50 50 25 12 25 25 Width [mm] 510 510 1,500 1,5001,500 1,500 1,500 Change rate MD [%] 0.05 0.1 0.05 0.19 0.11 0.91 0.5Change rate TD [%] 0.02 0.04 0.02 0.08 0.04 0.81 0.4 Windingtension/change rate MD 1,250 1,250 1,250 625 310 625 625 Copper-cladlaminate Peeling strength [N/m] 17 16.9 17 18.6 17.5 18.1 17.1 ACresistance value [10⁻⁹ Ω · cm] 8.7 8.8 8.7 9.2 8.7 8.7 9.0 Evaluation ∘∘ ∘ ∘ ∘ ∘ ∘ Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Type offluororesin PFA1 PFA1 PFA1 (10) PFA1 (10) PFA1 PFA1 (20) PFA1 (10) PFA2(90) PFA3 (90) PFA2 (90) PFA2 (90) Molding condition Die width [mm]1,900 1,900 1,900 1,900 1,900 1,900 1,900 Forming rate [m/min] 10 10 1010 10 10 10 Annealing treatment conditions Temperature [° C.] 90 150 150150 Not Not Not Time [min] 5 5 15 15 carried carried carried Tension[N/m] 5 5 5 5 out out out Winding conditions [N/m] Tension [N/m] 62.5650 50 37.5 37.5 37.5 37.5 Roll film physical properties ConstructionMonolayer Monolayer Monolayer Monolayer Monolayer Monolayer Monolayerfilm film film film film film film Thickness [μm] 25 50 50 50 50 50 50Width [mm] 1,500 1,500 1,500 1,500 1,500 1,500 1,500 Change rate MD [%]0.99 1.0 0.04 0.03 1.2 1.7 1.3 Change rate TD [%] 0.75 0.94 0.02 0.020.88 1.1 0.72 Winding tension/change rate MD 625 1,250 1,250 1,250 31 2229 Copper-clad laminate Peeling strength [N/m] 18.3 17.9 16.9 17.7 16.51.7 17.1 AC resistance value [10⁻⁹ Ω · cm] 8.7 0.1 25 18 0.69 0.84 0.67Evaluation ∘ x ∘ ∘ x x x

In Table 1, the expression of “PFA1 (10), PFA2 (90)” in Ex. 10 meansthat PFA1 and PFA2 were used in combination respectively in proportionsof 10 mass % and 90 mass %. Other expressions in other Ex. and otherTables are used in the same manner.

Ex. 15

PFA1 was extruded into a film form by means of a 65 mmφ single screwextruder (manufactured by Toshiba Machine Co., Ltd., L/D=25, compressionratio of 3.1) having a T die having a width of 1,900 mm at a formingtemperature of 340° C. at a forming rate of 20 m/min to obtain a filmhaving a thickness of 25 μm and a width of 1,500 mm.

The film was subjected to annealing treatment by means of a bondingapparatus 200 having the construction illustrated in FIG. 2 and anannealing treatment apparatus 300 having the construction illustrated inFIG. 3 by the following procedure and wound to obtain a roll film havingthe film and a substrate laminated via an adhesive layer.

First, an untreated film 12 was conveyed from a first unwinding roll 201to bonding rolls 203 and 204 in the bonding apparatus 200, a substrate13 having an adhesive layer was conveyed from a second unwinding roll202 to the bonding rolls 203 and 204, and the untreated film 12 and thesubstrate 13 having an adhesive layer were bonded by the bonding rolls203 and 204 at room temperature, and the obtained laminate 14 was woundon a winding roll 205.

As the substrate for the substrate 13 having an adhesive layer, a filmhaving a thickness of 50 μm obtained by extruding pellets of PFA2 in theabove-mentioned manner was used. The adhesive layer was formed of aurethane acrylate adhesive into a thickness of 2 μm.

Next, the wound laminate 14 was transferred to an unwinding roll 301 inthe annealing treatment apparatus 300, unwound from the unwinding roll301, conveyed to a heating portion 302 with a tension of 5 N/m, heatedat the heating portion 302 under conditions of 150° C. and 5 minutes andwound on a winding roll 304 with a tension of at most 100 N/m to obtaina roll film. That is, the annealing treatment conditions were thetemperature of 150° C., time of 5 minutes and conveyance tension of 5N/m, and the winding condition was winding tension of at most 100 N/m.

The obtained roll film was unwound and cut into a length of 15 cm×widthof 15 cm, a copper foil having the same size was placed on a surface ofthe roll film side (surface of PFA1 side), and the substrate having anadhesive layer was peeled, followed by hot press by means of a vacuumpressing machine under conditions of 340° C., 15 minutes and 1.5 MPa toobtain a copper-clad laminate.

The obtained copper-clad laminate was subjected to the peeling test andthe electrolytic corrosion test. The results are shown in Table 2.

Ex. 16 to 21

A roll film was obtained in the same manner as in Ex. 1,5 except thatthe type of the fluororesin, the substrate and the annealing treatmentconditions (temperature, time and conveyance tension) by roll-to-rollprocess were changed as shown in Table 2, and a copper-clad laminate wasproduced and subjected to the peeling test and the electrolyticcorrosion test. The results are shown in Table 2.

TABLE 2 Ex. 15 Ex. 16 Ex. 17 Ex. 18 Ex. 19 Ex. 20 Ex. 21 Type offluororesin PFA1 PFA1 PFA1 PFA1 PFA1 PFA1 PFA1 Annealing treatmentconditions Temperature [° C.] 150 150 150 150 Not Not Not Time [min] 5 55 5 carried carried carried Tension [N/m] 5 10 5 5 out out out Roll filmphysical properties Construction With With With With With With Withsubstrate substrate substrate substrate substrate substrate substrateThickness [μm] 25 25 12 6 25 12 6 Width [mm] 1,500 1,500 1,500 1,5001,500 1,500 1,500 Change rate MD [%] 0.04 0.08 0.08 0.1 1.8 2.5 4.5Change rate TD [%] 0.02 0.04 0.04 0.08 1.0 1.8 2.8 Copper-clad laminatePeeling strength [N/m] 16.5 16.4 15.2 15.2 16.3 15.1 14.2 AC resistancevalue [10⁻⁹ Ω · cm] 8.9 8.8 5.4 5.4 0.7 0.3 0.1 Evaluation ∘ ∘ ∘ ∘ x x x

In Table 2, as the substrates 13 in Ex. 18 and 19, a film made of PFA2and having a thickness of 75 μm was used, instead of the film made ofPFA2 having a thickness of 50 μm.

Ex. 22

A co-extruded film having a two-layer structure was prepared by thefollowing procedure. PFA1 was melted at a preset temperature of 340° C.and supplied to a first manifold of a 400 m width two-layer multimanifold die by means of a 15 mmφ single screw extruder (manufactured byTanabe Plastics Machinery Co., Ltd.), ETFE1 was melted at a presettemperature of 340° C. and supplied to a second manifold by means of a30 mmφ single-screw extruder (manufactured by IKEGAI Corp.), and therespective molten resins were extruded into a film form from the multimanifold die at a forming rate of 2 m/min to obtain a co-extruded filmhaving a first layer (PFA1) having a thickness of 25 μm and a secondlayer (ETFE1) having a thickness of 75 μm and having a width of 320 mm.The co-extruded film was subjected to annealing treatment and wound inthe same manner as in Ex. 1 to obtain a roll film. The change rate MD ofthe roll film was 0.03, and the change rate TD was 0.02. The peelingstrength of a copper-clad laminate obtained by using the roll film was8.4 N/m, the AC resistance value was 8.4×10⁻⁹ Ω·cm, and evaluation was“◯”.

INDUSTRIAL APPLICABILITY

A highly reliable printed board which is suitable for high frequencydevices can be obtained by using the roll film of the present invention.

This application is a continuation of PCT Application No.PCT/JP2019/016355, filed on Apr. 16, 2019, which is based upon andclaims the benefit of priority from Japanese Patent Application No.2018-081794 filed on Apr. 20, 2018. The contents of those applicationsare incorporated herein by reference in their entireties.

REFERENCE SYMBOLS

11: melt, 12: untreated film, 13: substrate having an adhesive layer, 14and 15: laminate, 40 and 50: copper-clad laminate, 41 and 51: dielectriclayer, 42: copper layer, 52: first copper layer, 53: second copperlayer, 60: comb pattern, 61: line part, 62: base part, 71: sample, 72:power source, L: electrolyte, 100: production apparatus of untreatedfilm, 101: extruder, 102: T-die, 103: quenching roll, 104: cooling roll,105: nip roll, 106: winding roll, 200: bonding apparatus, 201: firstunwinding roll, 202: second unwinding roll, 203 and 204: bonding roll,205: winding roll

What is claimed is:
 1. A roll film comprising a melt-processablefluororesin as the main component and having a thickness of from 1 to100 μm, the dimensional change rate of which is less than 1.0%, in termsof an absolute value, in each of MD and TD, when heated at 150° C. for30 minutes and then cooled to 25° C., based on the dimension at 25° C.2. The roll film according to claim 1, wherein the ratio of the tensionwhen wound to the dimensional change rate, in terms of an absolutevalue, in MD is from 100 to 1,000,000.
 3. The roll film according toclaim 1, which is used for a copper-clad laminate.
 4. The roll filmaccording to claim 1, wherein the melt-processable fluororesin is afluororesin having units derived from tetrafluoroethylene and unitsderived from a perfluoro(alkyl vinyl ether).
 5. The roll film accordingto claim 1, wherein the melt-processable fluororesin is a fluororesinhaving a functional group having an ion scavenging function.
 6. The rollfilm according to claim 1, which comprises a melt-processablefluororesin having a functional group having an ion scavenging functionand a melt-processable fluororesin other than the above hot-meltfluororesin as the main component.
 7. The roll film according to claim1, which has a layer of the melt-processable fluororesin and a layer ofa melt-processable fluororesin having a functional group having an ionscavenging function.
 8. The roll film according to claim 5, wherein thefunctional group having an ion scavenging function is at least onemember selected from the group consisting of a carbonyl group, a carboxygroup, a carboxylic acid anhydride group (—C(═O)—O—C(═O)—), acarboxylate group, a sulfonyl group, a sulfo group and a sulfonic acidanhydride group (—S(═O)₂—O—S(═O)₂—).
 9. The roll film according to claim1, which has a thickness of from 3 to 75 μm.
 10. A method for producingthe roll film as defined in claim 1, which comprises subjecting a filmcomprising the melt-processable fluororesin as the main component andhaving a thickness of from 1 to 100 μm to annealing treatment at from atemperature lower by 210° C. than the melting temperature (Tm) of themelt-processable fluororesin to a temperature lower by 20° C. than Tmand then winding the film.
 11. The method according to claim 10, whereinthe annealing treatment is carried out with a tension of at most 10 N/mapplied to the film.
 12. The method according to claim 10, wherein thefilm is wound with a tension of at most 500 N/m applied on the film. 13.A method for producing a copper-clad laminate, which comprises unwindingthe roll film as defined in any one of claim 1 and forming a copperlayer on a surface of the unwound film.
 14. The method according toclaim 13, which forms a copper layer having an AC resistance value ofhigher than 1.0×10⁻⁹ Ω·cm.
 15. A method for producing a printed board,which comprises producing a copper-clad laminate by the method asdefined in claim 13 and etching the copper layer to form a patternedcircuit.